Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$78.65	6.123%	$83.4657	$83.47	$83.45	$83.50
Purchase #2	$10.67	10.792%	$11.8215	$11.82	$11.80	$11.80
Purchase #3	$27.78	6.567%	$29.6043	$29.60	$29.60	$29.60
Purchase #4	$108.98	3.219%	$112.4881	$112.49	$112.50	$112.50
Purchase #5	$162.83	11.212%	$181.0865	$181.09	$181.10	$181.10
Purchase #6	$121.26	8.163%	$131.1585	$131.16	$131.15	$131.20
Purchase #7	$220.84	3.169%	$227.8384	$227.84	$227.85	$227.80
7 purchase totals =	$731.01		$777.4630	$777.47	$777.45	$777.50